1. Field of the Invention
The present invention relates to a control apparatus for an injection molding machine and more particularly to such a control apparatus which displays a numerical value data set externally and allows an operator to operate while directly viewing the data.
2. Description of the Prior Art
Conventionally, in order to properly perform a desired molding operation, a control apparatus for an injection molding machine controls the operation of the machine using data on various numerical values and monitors and adjusts the actual operating state of the injection machine.
In order for the operator to set, adjust and confirm data on various numerical values quickly and surely, the applicants have proposed a control apparatus for an injection molding machine in which the indication of a control panel, the disposition of operating elements and the correspondence between the operating elements are easily understood to thereby improve visuality and operability (Japanese Patent Application No. 58-32581).
FIG. 9 shows a control apparatus for an injection molding machine which includes a main processing system connected with a bus-line BUSL1 and subprocessing systems connected with bus-lines BUSL2 and BUSL3.
The bus-line BUSL1 is connected with a main processing unit 115; a common RAM 125; output units 121, 124; control panels 111, 112 through interfaces 11,, 114, respectively; input units 118, 119 of the injection molding machine through A/D converters 117, 120, respectively; and a sequencer 123 through an I/O unit 122.
The main processing unit 115 includes an internal memory (not shown) backed up by a battery 116 and stores various numerical value data which are exchanged through the bus-line BUSL1. The main processing unit 115 includes a non-volatile program memory which stores programs for processing various data, generates operation commands in accordance with settings on the control panels 111, 112 and inputs from the input units 118 and 119, and outputs them to the output units 121, 124 to control the injection molding machine.
The control panels 111, 112 each include an operating unit for setting and adjusting data and a display for displaying the set data. Data necessary for the injecting operation is set in the control panel 111 while data necessary for the clamping operation is set in the control panel 112.
The input units 118 and 119 each detect the executing state of the injection molding machine. The input unit 118 obtains status signals related to the injecting operation by means of an injection pressure sensor 118A, a linear scale 118B for detecting the position of a screw in the injecting operation and a tachometer 118C for detecting the rotational speed of the screw required in conjunction with the metering process. The input unit 119 obtains status signals related to the clamping operation by means of a clamping pressure sensor 119A and a linear scale 119B for detecting the position of a moving mold.
The output units 121, 124 each perform a D/A converting operation on an operation command signal from the main processing unit 115. The output unit 121 actuates a valve device 121A such as an electromagnetic flow valve or a relief valve provided in the injection portion of the injection molding machine in accordance with a command for the injecting operation. The output unit 124 actuates a valve device 124A provided in the clamping portion of the machine in accordance with a command for the clamping operation.
The sequencer 123 obtains signals from detectors 130 such as limit switches disposed at the respective particular elements of the injection molding machine during the injection and clamping operations and provides control of the interlocking relationship between the respective elements.
The common RAM 125 also connected with the bus-lines BUSL2 and BUSL3 is a buffer memory which is used for mutual exchange of data between the respective elements connected with the bus-lines BUSL2 and BUSL3 and the main processing unit 115.
The elements connected with the bus-line BUSL2 are a sub-processing unit 126; a printer 127 through an interface 137; a production management information setting unit 128 through an interface 135; a control panel 129 through an interface 136; and a sequencer 123 through an interface 134.
The sub-processing unit 126 includes an internal memory (not shown) backed up by a battery 133 and stores molding data-mass corresponding to a used mold. The sub-processing unit 126 is also connected to an external storage medium such as a magnetic tape device 132 to thereby load a data group corresponding to the used mold and to save changed a data group. The sub-processing unit 126 employs a system for beforehand storing a data group corresponding to a plurality of molds or a system for sequentially loading a data group corresponding to each of the molds to be used.
The printer 127 prints out a data group stored in the common RAM 125 or in the sub-processing unit 126.
The production management information setting unit 128 designates a mold to be used for molding and sets the number of shots of moldings molded by that mold.
The control panel 129 controls loading data in the sub-processing unit 126 and data transfer between the sub-processing unit 126 and the main-processing unit 115 and sets and displays a molding cycle time corresponding to a mold and moldings produced thereby and also displays an injection cycle time and a time required for blowing air against the mold.
The sequencer 123 outputs to the injection molding machine an alarm signal indicative of overtime when a time (for example, a first molding cycle time) set on the control panel 129 is exceeded.
The elements connected with the bus-line BUSL3 are the subprocessing unit 139; a control panel 142 through an interface 140; and thermometers 130 disposed at the particular elements of the molding machine through an interface 141 to thereby constitute a temperature controller 138.
The subprocessing unit 139 monitors, for example, the temperature of oil within the hydraulic unit and the actual temperature within the resin melting cylinder from the thermometers 130 and adjusts the temperature of the molding machine in accordance with a setting at the control panel 142 and a preset program.
In the control apparatus, the respective displays and operating units in the control panels 111, 112, 129 and 142 are arranged in such a manner that the operator can visually confirm the advancement of the molding operation properly.
As shown in FIG. 10, the control panel 111 digitally displays various data by means of LEDs. Displayed data are collected for each system to improve readability for confirmation and operation. Main data such as injection pressure 172, screw position 169 and screw rotational speed 167 are displayed on large displays for ease of visual confirmation. Digital switches are used to permit digital display and adjustment of the values of data 151-158, 160-164, 166, 170, 171, 173-178 which require confirmation, adjustment and setting.
For those digital switches, the applicants have proposed an electronic digital switch unit in which numerical values held by registers are displayed by means of LEDs and push buttons disposed above and below the displays are used to increases and decrease the numerical values (see Japanese Patent Application No. 59-174171).
There are other digital switches in which respective place modules are connected to provide a required number of places where necessary. There are also switches in which respective modules are connected by signal lines to easily take a figure up/down one place automatically.
The respective positions of displayed places are set appropriately when required in digital switches in the control panels of the control apparatus for the above mentioned conventional injection molding machine.
For example, if the number of displayed places is 3, where two places are used for an integer part and one place for a decimal part, the displayed numerical value is 0.0-99.9, so that numerical values in a range of 0-100 can be handled in units of 0.1. If one place is used for the integer part and two places are used for the decimal part, a displayed numerical value is 0.00-9.99, so that numerical values in a range of 0-10 can be handled in units of 0.01.
Since operation buttons corresponding to the positions of displayed places set numerical values in the digital switches of the conventional control apparatus, however, the buttons are fixed at preset positions of places for mutual correspondence, so that various inconveniences will occur in use.
For example, if handling three significant figures is considered, a numerical value in a range of 0-100 is required to be handled in units of 0.01 in order to cover numerical values such as 1.23 and 12.3. In order to cope with this in a fixed-point system, a display such as 01.23-12.30 is required to be implemented using four figures. Therefore, as the number of places increases, cost, scale and space for installation increase while some ineffective places are produced among the set displayed places.
When various numerical value data are accommodated in a fixed board region to show all the pieces of data, an increase in the number of displayed places in the digital switch is a big obstacle to the arrangement.
It is an object of the present invention to provide a control apparatus for an injection molding machine which ensures a sufficient range and accuracy of numerical data displayed or set with a small number of displayed places.